Kosan181
XS400 Enthusiast
How much rpm is it supposed to go to?
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Low speed, won't rev higher than 5k and won't do above 45
- Thread starter Kosan181
- Start date
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- Tags
- carb setup engine
new kid on the brat
new kid on the brat
That's good news but what jets we're in it before. And what size are your main jets.
Kosan181
XS400 Enthusiast
It was stock jets (132.5) and I went up to 142.5. now I think I may order some pilot jets because it still does have some trouble starting when it's cold.
new kid on the brat
new kid on the brat
Ahh sweet. I thought that said 42.5, as in idle jets. My 1980 had 45 idle jets 135 mains. Upping the idle jets will help the starting. I usually buy the next two sizes up.you want your fuel mixture screws to have the highest rpm when they are 1 1/2 to 2 1/2 turns out. On the main jets Keep uping the jet size till the performance drops. Then you will know your too rich. Then drop a size and ride it a while. When you get used to the way it runs drop another size and see what happens. Im kind of a fanatic about tuning. These are way easier to tune than a two stroke. Make sure your points are clean, and set,set the timing,and then dial the points in so they both fire at the right time. Set the valves, then dial the carbs in again.
new kid on the brat
new kid on the brat
new kid on the brat
new kid on the brat
When you have your carbs off,look into the butterfly end of the carb, there will two to three tiny holes in the carb body, right at the edge of the butterfly, these are the idle circuit ports. As you begin to open the throttle the air velocity will start to raise the slide. This is the transition period between idle and main circuit.1/16th to 1/8th of the throttle range. If your idle jets are too small, you will have a hesitation. To rich and it will bog. Sometimes hard to tell the difference.
Kosan181
XS400 Enthusiast
Wow dude thanks, that really in depth and helpful!
new kid on the brat
new kid on the brat
These bikes were not designed to turn 10,000 rpm. Your going to run out of power around 8,000 rpm unless you change cams and port the head. And this will just sacrifice the bottom end power. Running open exhaust will also sacrifice power.
Kosan181
XS400 Enthusiast
Okay, good. I'm running 8k in RPM and have way more power than before. Now I think I just need to get my idle tuned properly and I'll be set.
Kosan181
XS400 Enthusiast
Also do you know how much oil is supposed to be in the engine?
Right on the side engine case it should say, 2000cc. One quart=1000cc. You also can not check oil level while the bike is on the kickstand. Its gotta be standing straight up and/or on the center stand.
